Macrophages are sentinel cells that play a pivotal role in a broad range of innate and adaptive immune responses. Macrophages can be infected by HIV-1 and because these are long-lived cells and are resistant to the cytopathic effects of virus infection, contribute significantly to the virus reservoir throughout the course of the disease. Macrophages are present ubiquitously in all tissues and can disseminate virus to CD4+ T cells across cell-to-cell junctions with high efficiency. In this proposal, we will test the hypothesis tat establishment of productive infection in macrophages by HIV-1 and de novo viral protein expression triggers type I IFN-dependent pro-inflammatory responses. Using a proviral mutagenesis and expression strategy, we will identify the viral determinants that are necessary for inducing innate responses. We will utilize immuno-affinity purification and mass spectrometry approaches to identify the host factor(s) that detects these pathogen determinants and the signaling cascades that are triggered upon engagement of the viral determinants by this yet to be identified host factor. Finally, we will determine if induction of innate responses enhances expression of interferon-stimulated genes, such as CD169, that are subverted by HIV-1 to facilitate virus spread to CD4+ T cells across infectious synapses, a macrophage-dependent mechanism of systemic virus dissemination.